Thermochemistry (1)(1) - All matter contains energy so whenever matter undergoes a change the quantity of energy that the matter contains also changes

# Thermochemistry (1)(1) - All matter contains energy so...

This preview shows page 1 - 9 out of 56 pages.  Two forms of Energy Transfer Work (w) Work = force x distance Force (newton) = mass x acceleration = kgm/s 2 Work = (kgm/s 2 )(m) = kgm 2 /s 2 = joule Work can also be done by a gas with the equation W = -P V Heat (q or Q) transfer of thermal energy between two bodies that are different temperatures Measured in joules Temperature = Thermal Energy Energy, Heat, and Work You can think of energy as a quantity an object can possess or as a collection of objects. You can think of heat and work as the two different ways that an object can exchange energy with other objects. Either out of it, or into it The amount of kinetic energy an object has is directly proportional to its mass and velocity. KE = ½ mv 2 Units of Energy When the mass is in kg and velocity is in m/s, the unit for kinetic energy is . 1 joule of energy is the amount of energy needed to move a 1 kg mass at a speed of 1 m/s. One joule in everyday life represents approximately: the energy required to lift a small apple (weighing approximately 100 g) vertically through one meter. the energy released when that same apple falls one meter to the ground. the heat required to raise the temperature of 1 g of water by 0.24 K. the typical energy released as heat by a person at rest, every 1/60th of a second. the kinetic energy of a 50 kg human moving very slowly (0.2 m/s). the kinetic energy of a tennis ball moving at 23 km/h (6.4 m/s). System vs Surroundings In any thermodynamic study, the first step is to define the system . System – the actual physical or chemical change taking place Open system, closed system or isolated system Surroundings – the rest of the universe outside of the system In chemistry we usually study the system (the reaction) and most reactions are a closed What we study is the exchange of energy between the system and the surroundings open closed isolated 8 First law of thermodynamics – energy can be converted from one form to another, but cannot be created or destroyed. Chemical energy lost by combustion = Energy gained by the surroundings system surroundings Can test the 1 st law by measuring only the change in the internal energy of a system between its initial state and its final state in a process. E Change in Internal Energy  #### You've reached the end of your free preview.

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